Add-on for injector pen



FIG. 1 is a front perspective view of an add-on for injector pen showing my new design.

FIG. 2 is a top plan thereof.

FIG. 3 is a bottom plan view thereof.

FIG. 4 is a right side elevation view thereof.

FIG. 5 is a left side elevation view thereof; and,

FIG. 6 is a back plan view thereof.

The broken lines are included for the purpose of illustrating portions that form no part of the claimed design. 

CLAIM The ornamental design for an add-on for injector pen, as shown and described. 